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README.md

thenify

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Promisify a callback-based function using any-promise.

  • Preserves function names
  • Uses a native promise implementation if available and tries to fall back to a promise implementation such as bluebird
  • Converts multiple arguments from the callback into an Array, also support change the behavior by options.multiArgs
  • Resulting function never deoptimizes
  • Supports both callback and promise style

An added benefit is that thrown errors in that async function will be caught by the promise!

API

fn = thenify(fn, options)

Promisifies a function.

Options

options are optional.

  • options.withCallback - support both callback and promise style, default to false.
  • options.multiArgs - change the behavior when callback have multiple arguments. default to true.

    • true - converts multiple arguments to an array
    • false- always use the first argument
    • Array - converts multiple arguments to an object with keys provided in options.multiArgs
  • Turn async functions into promises

    var thenify = require('thenify');
    
    var somethingAsync = thenify(function somethingAsync(a, b, c, callback) {
    callback(null, a, b, c);
    });
    
  • Backward compatible with callback

    var thenify = require('thenify');
    
    var somethingAsync = thenify(function somethingAsync(a, b, c, callback) {
    callback(null, a, b, c);
    }, { withCallback: true });
    
    // somethingAsync(a, b, c).then(onFulfilled).catch(onRejected);
    // somethingAsync(a, b, c, function () {});
    

or use thenify.withCallback()

var thenify = require('thenify').withCallback;

var somethingAsync = thenify(function somethingAsync(a, b, c, callback) {
  callback(null, a, b, c);
});

// somethingAsync(a, b, c).then(onFulfilled).catch(onRejected);
// somethingAsync(a, b, c, function () {});
  • Always return the first argument in callback

    var thenify = require('thenify');
    
    var promise = thenify(function (callback) {
    callback(null, 1, 2, 3);
    }, { multiArgs: false });
    
    // promise().then(function onFulfilled(value) {
    //   assert.equal(value, 1);
    // });
    
  • Converts callback arguments to an object

    var thenify = require('thenify');
    
    var promise = thenify(function (callback) {
    callback(null, 1, 2, 3);
    }, { multiArgs: [ 'one', 'tow', 'three' ] });
    
    // promise().then(function onFulfilled(value) {
    //   assert.deepEqual(value, {
    //     one: 1,
    //     tow: 2,
    //     three: 3
    //   });
    // });